Development of an improved calibration method for the LFB ultrasonic material characterization system

We investigated standard specimens for accurately calibrating the line-focus-beam ultrasonic material characterization (LFB-UMC) system without system dependencies. We evaluated several types of lithium tantalate (LiTaO3) substrates using two LFB-UMC systems with different device/system characteristics to measure and calibrate the propagation characteristics of the leaky surface acoustic waves (LSAWs), and analyzed the variations between the calibrated results. We concluded from this analysis that, by selecting materials with the cut surfaces and propagation directions of standard specimens that are identical to the objects to be calibrated, calibration errors resulting from different performance characteristics between the two systems could be nearly eliminated. Also, analytical errors caused by the effects of spectra with two close peaks (another propagation wave mode), one of the most common problems of characterization in the past, could be eliminated at the same time by this method.     

Preparation of highly flexible chitin nanofiber-graft-poly(γ-l-glutamic acid) network film

In the previous study, we successfully prepared a chitin nanofiber film by regeneration from a chitin ion gel with an ionic liquid using methanol. In this study, we performed surface-initiated graft polymerization of γ-benzyl l-glutamate N-carboxyanhydride (BLG-NCA) from amino groups on a partially deacetylated chitin nanofiber (PDA-CNF) film. First, the chitin nanofiber film was immersed in 40 % NaOH aq. at 80 °C for 7 h for partial deacetylation. Then, the PDA-CNF film was immersed in a solution of BLG-NCA in ethyl acetate at 0 °C for 24 h for graft polymerization from amino groups on nanofibers to give a chitin nanofiber-graft-poly(γ-benzyl l-glutamate) (CNF-g-PBLG) film. The analytical results of the film indicated that graft polymerization of BLG-NCA occur on surface of nanofibers. Furthermore, the film was treated with 1.0 mol/L NaOH aq. to convert PBLG on nanofibers into poly(γ-l-glutamic acid sodium salt) (PLGA). Then, condensation of the resulting carboxylates with amino groups at the terminal ends of PLGAs or the remaining amino groups on nanofibers was performed using the condensing agent to produce a CNF-g-PLGA network film. The resulting film showed the good mechanical properties with high flexibility, which has potentials as promising materials for practical applications.     

Scalability of spectrum-sliced DWDM transmission and its expansion using forward error correction

This paper clarifies the scalability of spectrum-sliced dense wavelength-division-multiplexing (DWDM) transmission systems primarily intended for metro access applications. A theoretical analysis elucidates the tradeoff between the loss budget and the sliced bandwidth (i.e., the number of channels with assuming light sources with a fixed bandwidth). Moreover, the use of forward error correction (FEC) to expand scalability is studied. Based on the analysis, two spectrum-sliced DWDM transmission schemes are introduced. One demonstrates 1.25-Gb/s, eight channel spectrum-sliced DWDM transmission through the use of directly modulated super-luminescent diodes (SLDs), and the other confirms 10-Gb/s, eight channel spectrum-sliced DWDM transmission with the channel spacing of 200 GHz through the use of FEC.     

Stoichiometry of III–V compounds

Effects of stoichiometry control on electrical, optical and crystallographic features in III–V compounds are shown. The application of the optimum vapor pressure during annealing and crystal growth is shown to minimize the deviation from stoichiometric composition. Temperature-dependence of the optimum vapor pressure is also obtained. In view of the defect formation mechanism, existence of the stable interstitial arsenic atoms (I_As) in GaAs is emphasized. The mechanism of stoichiometry control is discussed on the basis of the equality of chemical potentials and the change of saturating solubility in the liquidus phase as a function of the vapor pressure.     

Geranial: the alarm pheromone in the nymphal stage of the oribatid mite,Nothrus palustris

The presence of an alarm pheromone was demonstrated in the deutonymphal stage of the oribatid mite, Nothrus palustris (C. L. Koch). The active principle was identified as 3,7-dimethyl-(E)-2,6-octadienal, geranial, and was shown to be active at doses of 10–100 ng. This is the first such pheromone identified in oribatid mites.     

n- and p-Channel field-effect transistors based on diquinoxalinoTTF derivatives

Three new quinoxalinoTTF derivatives with methyl, trifluoromethyl and fluoro groups were synthesized and characterized by UV–vis absorption spectroscopy, differential scanning calorimetry, X-ray single crystal analysis, X-ray diffraction, and field-effect transistor (FET) characteristics. All of them have π-stacking structures in the single crystals. The quinoxalinoTTF derivative with trifluoromethyl groups exhibited an n-type FET, which is a rare example of n-channel FETs based on TTF derivatives. The highest electron mobility is 0.01 cm² V^?1 s. The FET polarity was converted to p-channel from n-channel by replacing the trifluoromethyl groups with methyl groups. The hole mobility is as high as 0.2 cm² V^?1 s. In contrast, the fluoro substituted derivative did not show FET properties due to the poorly ordered molecular arrangement.     

Dynamic fluorescence quenching precedent to thermally-induced phase separation of poly(ethoxyethyl vinyl ether) aqueous solution

We focused on the stage preceding the thermally-induced phase separation of aqueous solution of poly(ethoxyethyl vinyl ether) (PEVE). Previously, we observed an interesting dynamic quenching just below the phase separation temperature. The dynamic fluorescence quenching disappeared by addition of a surfactant. In systems without the phase separation of both the hexane solution of PEVE and the PEVE bulk, the fluorescence lifetime decreased monotonically with the increase of temperature. These results indicated that the marked decrease is due to the dynamic quenching by the collision between the fluorescent probe and the PEVE segment induced by the thermal fluctuation precedent to the phase separation.